The overall objective of this project is to evaluate maternal immunization for prophylaxis against infectious diseases in neonates and infants. Passively acquired humoral immunity for protection of neonates and young infants against a wide variety of bacterial and viral pathogens is extremely important. Within the infant itself, humoral immunity develops early in ontogeny but is relatively inefficient. By birth the infant is capable of responding to a large number of antigens, but there is little response to some antigens; e.g. polysaccharide antigens. This particular lack of response is significant in that young infants are at substantial risk for infections caused by capsulated organisms such as the group B streptococci (GBS) and H. influenzae type b (Hib). While significant progress has been made in the development of more immunogenic bacterial and viral vaccines, prophylaxis in the vulnerable neonate and young infant remains problematic. Strategies for protecting this group against infection require evaluation of alternative delivery approaches. The theory behind maternal immunization is that sufficient antibody directed against organism components (e.g. type-specific capsular polysaccharides of GBS and Hib) can protect against systemic infection, and that antibody elicited by vaccination of women could confer protection to their infants through placental transfer. Maternal immunization has therefore been proposed as a method of providing short-term passive immunity, obviating the need for neonatal immunization when it is less likely to be effective. The work in this contracts encompasses Phase I and Phase II clinical trials of candidate vaccines of various types.